Thermionic tube



Aug. 30, 1932. I L, BHARD 1,874,182

THERMIONIC TUBE Filed Dec. 3, 1928 INVENTOR. QoM/b a gefjfvu),

ATTORNEY Patented Aug. 30,1932

UNITED STATES PATENT oar-ice LOUIS A. GEBHA BD, OI WASKINGTON,- DI8TBICT OI conmn, ASSIGROB 'ro m RADIO, INC, 0] YORK, N. Y. A. CORPORATION 01' nmwm 'I'KEBKIONIC TUBE Application fled December 8, 1988. Serial Io. 888,587.

My invention relates broadly to thermionic tubes and more specifically to thermionic the deener ization of thermionic tubes not needed un er suchconditions.

A better understanding of the thermionic tube system of my invention will be had by referring to the specification following and the accompanying drawings wherein, Figures 1, 2, 3 4 and 5' are illustrations showing the thermionic tube of my invention.

In the operation of thermionic tubes a cathode is'caused to emit electrons which are radiated fromthe cathode to another elec-' trode generally referred to as the anode. A mesh-work of wires is sometimes employed between these two electrodes the purpose of which is to control the electronic current between the cathode and anode. The bombardment of the anode ives rise to 'exoessive temperature on the ano e. This temperature is proportional to the relative size of the electrodes, the circuit associated with the tube and the anode potential supplied from a given source. A temperature of excessive value causes disintegrating of the anode and destruction of the tube. As is ordinarily the practice an increase in the power of a transmitter or the output of a bank of rectifiers is accomplished by a roportional increase in the potential supplied the anode or the input of the rectifier. This is a convenient method for the control of such systems but many disadvantages arise from such practice. The greatest danger is that of overloading the tube. The greatest disadvantage lies in the fact that a tube having a rating for maximum power seldom functions efficiently on reduced power input. The efiiciency in operation is therefore reduced and the expense is unnecessarily out of proportion to the power output of the system. In the thermionic tube system of. my invention the above mentioned dangers are avoided and the disadvantages overcome. A better understanding can be had of the system I employ by referring to the accompanying drawings.

Fig. 1 shows a composite side elevation and cross-section of one form of the thermionic tube of my invention. An envelope 1, usually of glass or suitable silicate composition, encloses a cathode 2, anode 3 and control electrode 4. Conductor wires from these electrodes are sealed through the stem 10. A bi-metallic member 5 is provided in connection with anode 3. Bi-metallic member 5 may comprise an two dissimilar metals or alloys having di erent coeflicients of expansion. One end of bi-metallic member 5 is adjacent to anode 3. The opposite end carries a contact member 6. Contact member 7 is ositioned adjacent to C(mtnnt member 6 and may be supported by a seal through the envelope 1 or supported by the stem 10. A s ring 8 is associated with contact member 7 t e function of which is to prevent damage to the envelope 1 and bi-metallic member 5 when the temperature is in excess of the value necessary to establish connection between contact members 6 and Fig. 2 shows another. modification of the thermionic tube of my invention. The reference characters in this illustration corres ml with those shown in Fig. 1. A secon bimetallic member 5a is herein employed provided with contact member 6a and adjacent to contact member 7a. Contact member 7a is su ported by means of a seal in envelope a purpose similar to Fig. 1. The bi-metallic members shows another modification of the thermionic I tube of my invention. The reference characters in this illustration correspond to those 20 "spring 10. I The other end of coil spring shown in Figs. 1 and2. Bi-metallic member 5 is herein shown in the form of a spiral. Such an arrangement is more sensitive to minute changes in temperature as it also more readily responds to such changes. Contact member 7 is positioned adjacent to contact member 6 and is supported by the seal in stem 10. The support for contact member 7 may be iimilar to the support for contact member 7 in i 2.

Figs. 4 and 5 show further modifications of the thermionic tube system of my inven tion. The reference characters herein correspond to those previously referred to in the foregoing illustrations. In Fig. 4, bi-metallic member 5 is similar to bi-metallic member 5 of Fig. 1 and comprises two dissimilar metals as alloys thereo one end of which is adjacent to anode 3. The op osite end of bi-metallic member 5 is associated with a is connected to movable member 9. Movable member 9 comprises a length of suitable insulating material or may comprise metal or alloy thereof when an insulated circuit is not desired. One end of movable member 9 is supported by asuitable pivot and bearing on anode 3. T e opposite end of movable member 9 isprovided with a contacting member 6. Contact member 7a is positioned adjacent to contact member 6 and provided with suitable shockabsorbing spring 8a. The support for contact member 7 a is shown as the seal in envelope 1, however, the support may be through the seal in the stem 10. Contact 7 is positioned equidistant from the pivot of movable member 9 and on the opposite side of the pivot in respect to contact 7a. This arrangement comprises a toggle switch when movable member 9 may establish connection with either contact 7 or contact 7a.

-The arrangement in Fig. 5 is quite similar to the arran ement shown in Fig. 4. In this illustration i-metallic member 5 comprises a spiral similar to bi-metallic member 5 of Fig. 3. To-the outside end of spiral bi-metallic member 5 there is connected one end of coil spring 10. The movable member 9 is provided with contact members 6 and'contact members 7 and 7 a are provided simi- 'lar to those shown in Fig. 4. A double contact is here provided comprising contact members 7a and 7b with associated spring member's 8a and 8?), respectively. Contact members adapted to contact with members 7 a and 7?), may be electrically connected whereby an electrical circuit including members 7 a and .7 b is completed. As shown in Fig. 4. additional contact members 7 may be provided operatively related to contact member 6 of movable member 9. I

The operation of the thermionic tubes of my invention illustrated in Figs. 1 to 3 in elusive is as follows. Bi-metallic member 5 responds to changes in the temperature of anode 3 and the free end swerves toward or away from contact members 7 or 7a. In Fig. 4, bi-metallic member 5 responds to changes in the temperature of anode 3 and the free end of member 5 swerves toward the horizontal plane. It is arbitrary whether bimetallic member 5 is mounted vertically or horizontally. The free end of bi-metallio member 5 is associated with a coil spring 10. The other end of coil spring 10 is connected to movable member 9. As the free end of himetallic member 5 swerves toward the horizontal plane the movable member 9 will be caused to connect with either of contact members 7 or 7a. Thus an increase of temperature causes a complete electrical circuit by means of contact member 7a or by contact member 7. A decrease in the temperature of anode 3 would cause the circuits to be established in the reversed order. The operation of the arrangement shown in Fig. 5 is quite similar to that of Fig. 4. In this arrangement bi-metallie member 5 is in the form of a spiral thus affording a more sensitive control than that from the member illustrated in Fig. 4.

.employed with the addition of contact member 7 a. Contact member 6 is designed to short circuit contact members 7a and 7a thereby completing an electrical circuit in which these members may be included. Contact member 7 may therefore be insulated from movable member 9 to provide a circuit independent of anode 3.

I realize that many modifications of the thermionic tube construction of my invention are possible. For instance, the abnormal heating of one tube can automatically cause proper circuit breakers to disconnect this tube and connect a second tube in the same circuit as the first. The bi-metallic member may be caused to swerve away from a positioned contact in response to an increase in the temperature of the anode. Any number of contact members may be employed with thermionic tubes having any number of electrodes. It is to be understood that my invention is not limited by the foregoing specification or accompanying drawings and that modifications of my invention will readily. suggest themselves to those skilled in the art. All such modifications are intended to be included within the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as fol- 2. An electron tube comprising an enclosing vessel including an anode and cathode, a bimetallic thermo-expansive member having one end fixed on said anode, a pivotally mounted switch, a spring having one end connected to the free end of said member and the other end connected with said switch at a point remote from the pivot and independent resilient contacts disposed in the path of said switch whereby the switch is shifted from one Contact to another with a snap action according to the operation of said bimetallic thermo-expansive member.

3. A thermionic tube including a cathode, a control electrode and an anode, aspirally formed bi-metallic strip having its inner end thermally connected with said anode in a position centrally thereof, an angularly movable arm pivotally connected to said anode,

2 contacts carried by said arm, a plurality of independent contacts disposed in the path of the contacts on said arm, and a spring member interconnecting said arm and the movable end of said bi-metallic strip for effecting a displacement of the contacts on said arm' with respect to said independent contacts in accordance with the thermal operation of said bi-metallic strip. LOUIS A. GEBHARD. 

